A type of such control apparatuses set forth above, for example, disclosed in U.S. Pat. No. 7,256,561 corresponding to Japanese Patent Application Publication No. 2006-174697, is designed to carry out a method of driving a converter circuit for a rotating electrical machine under model predictive control.
Specifically, the control apparatus disclosed in the US Patent Publication temporarily determines switching state sequences for each of switching state combinations at each of N sampling times from a start sampling time k; these N sampling times are expressed as k, k+1, k+2, . . . , k+N−1 (N≧1). Then, for each of the switching state sequences, the control apparatus calculates a torque trajectory of the rotating electrical machine from the starting sampling time k up to the sampling time k+N.
Next, the control apparatus predicts, by extrapolation, a following torque trajectory based on the torque trajectory from the sampling time k+N−1 to k+N of each of switching state sequences.
For each of the switching state sequences, the control apparatus determines the number of times n until the extrapolation values of the predicted following torque trajectory is outside a preset range.
Next, for each of the switching state sequences, the control apparatus divides, by the number of times n, a number of switching transitions defined by a corresponding one of the switching state sequences.
Then, the control apparatus determines, as an actual switching state at the sampling time k, the switching state at the sampling time k with which the corresponding switching state sequence has the smallest divided value.
This control apparatus set forth above may reduce the number of switching transitions of the converter circuit.